A common trend in machine design, particularly in the office equipment industry, is to organize a machine on a modular basis, wherein certain distinct subsystems of the machine are bundled together into modules which can be readily removed from the machine and replaced with new modules of the same or similar type. A modular design facilitates great flexibility in the business relationship with the customer. By providing subsystems in discrete modules, also known as “customer replaceable units” or CRUs, visits from a service representative can be made very short, since all the representative has to do is remove and replace a defective module. Actual repair of the module may take place remotely at the service provider's premises. Further, some customers may wish to have the ability to buy modules “off the shelf,” such as from an equipment supply store. Indeed, it is possible that a customer may lease the machine and wish to buy a supply of modules as needed. Further, the use of modules, particularly for expendable supply units (e.g., copier and printer toner bottles) are conducive to recycling activities.
For example, U.S. Pat. No. 3,985,436 to Tanaka, et al., which is incorporated by reference herein in its entirety, describes an electrophotographic copying apparatus in which a photoreceptor, a developing device and a cleaning device for residual toner particles are integrally incorporated in a casing as one unit so as to be releasably inserted into the copying apparatus housing for efficient replacement and maintenance of such major components.
In order to facilitate a variety of business arrangements among manufacturers, service providers, and customers, it is known to provide these modules with electronically-readable memory devices, also known as “customer replaceable unit monitors” or CRUMs, which, when the module is installed in the machine, enable the machine to both read information from the CRUM and also write information to the CRUM. The information read from, or written to, the CRUM may be used by the machine to perform various functions. For example, U.S. Pat. No. 6,016,409 entitled “System For Managing User Modules in a Digital Printing Apparatus”, which is incorporated by reference herein in its entirety, describes various data that may be stored in a CRUM and various functions that may be performed using this data.
Various components within the CRUs, such as charging corotrons, transfer corotrons, and the like, require high voltage electrical power for operation. Typically, printing apparatuses such as electrophotographic copiers and printers will employ a single, host-mounted high voltage power supply unit to generate this high voltage power, and will conduct this high voltage electrical power to the CRUs via various conductors and terminals, contacts, etc . . . One of the failure modes of such printing apparatuses is erratic behavior and print quality defects due to breakdown of the insulation around the conductors that carry the high voltage electrical power from the host-mounted high voltage power supply to the component within the CRU. The breakdown of the insulation is typically caused by the effects of plasma, which is always present around high voltage wires. The problems caused by the breakdown of insulation are erratic with difficult to describe symptoms and, as a result, are very difficult for trained service engineers to troubleshoot.